The present invention relates to a method of transmitting real time data from a network element of a digital telecommunication network to a receiving server over a transmission link. The real time data are generated during operation of the network element and are collected in buffers located in transient memory of the network element and from the buffers the data are read out and transmitted over the transmission link. In the case that data transmission over the transmission link is disabled and the buffers are being filled, the data present in the buffers are flushed by being stored onto a permanent storage medium as backup data.
During operation of a network element, such as a switch or a cross connector, real-time data are generated which are intended for further processing by an external server. One example of such real-time data is the billing data which are generated by a switch of, e.g., a telephone network for each of the telephone connections processed. The billing data are then further processed by a billing application to calculate the individual charges billed to the users of the network. Formerly, the real-time data were gathered and stored on a medium by the network element and, in a separate step, the data were transferred via this medium to a processing station on which the processing application, such as the billing application, is run. Rather than this “offline” procedure, the present invention relates to the direct transfer of the real-time data to an external station.
The real-time data transfer allows fast spontaneous transfer of data over a link to an external receiving server for further processing, avoiding the need to store a substantial amount of data on the side of the network element. The receiving server need not actually be the processing station but can be an intermediate server which then transfers the data further to the processing station, without incurring any difference with regard to the present invention.
The real-time data to be transferred are generated continuously and are collected for the transfer to the application in buffers located in, for instance, transient memory. From there, the data are transmitted spontaneously; i.e., the data transmission is initiated by the sending station without specific request from the receiving side. The output of the data is done from the buffers via a transmission link employing, e.g., the well-known X.25 or IP protocols, often using a permanent connection. Thus, the transfer of data is performed directly between the network element and the application server and within a very short time, typically within a few seconds or minutes.
However, when used without a non-volatile backup system, this data transfer is not secure with respect to possible loss of data, which cannot directly be transmitted due to a fault, such as link failure or recovery of the receiving server, and stored for the duration of the fault. As the real-time data are generated as a consequence to the operation of the network element, the generation of new data to be transmitted is not stopped when a transmission failure occurs. When transmittal of data is not possible (“link outage”), further data are temporarily stored in transient memory buffers. When these buffers get full, newly generated data is lost until transmission becomes possible again.
One simple approach to increase security against data loss is to simply enlarge the number and/or size of the buffers; i.e., by increasing the total size of the transient memory reserved for temporary data storage. This method, which is independent of a backup system, increases the time before buffer overflow is reached in the case of link outage. However, the transient memory cannot be increased unlimited and, furthermore, this strategy enhances the risk that with a growing amount of data kept in transient memory, a large amount of data is eventually lost in case the sending server undergoes a failure recovery.
A known solution uses a backup system to increase the security of the real-time data transfer. When no output is possible over the link and all buffers in transient memory get full, all buffer contents are saved into a backup file on a permanent storage device, such as a hard disk. At a later time, the data are transferred to the receiving side by sending the backup file. Thus, transient memory space is made available again for the storage of further data that would otherwise be lost. However, there is no notification to the receiving side that some of the data are not sent, but rather saved into a backup file. The receiving server is required to poll if backup data need to be transferred. Furthermore, a separate link is necessary for the transfer of the backup file; e.g. via the FTAM service (“File transfer, Access and Management”) as defined by OSI standards or the well-known FTP transfer (“File Transfer Protocol”) based on the IP protocol. Moreover, the receiving server needs the software to receive the data and process the protocols with the backup data transfer, which represents a transmission mode well different from that of the real-time data transfer. Therefore, this solution enhances data security because it avoids the loss of data in case of a transmission fault such as a link failure, but it leads to a considerable overhead with respect to control and processing of the data to be received, as well as the hardware and software resources.
It is an aim of the present invention, therefore, to offer a backup system for real-time data transfer which avoids the above-mentioned disadvantages.